In terms of quantity this is a poor Cannes for British cinema. Quality-wise, it's a whole other matter. We Need to Talk About Kevin unveils at the morning seance with its budget seeded by the now-defunct UK Film Council; the production credit blinking in the darkness like the light from a star that's already upped and died. But the film's arrival heralds the rebirth of director Lynne Ramsay, who shot Ratcatcher in 1999, Morvern Callar in 2001 and then dropped clean off the map. She's been away too long.

We Need to Talk About Kevin is extraordinary – a maternal nightmare fired by a narrative that's not so much fractured as liquid; blending and folding its time-frame to mesmeric effect. Tilda Swinton is the middle-class American mum, toiling to process the actions of her sociopath son (Ezra Miller, positively sulphurous). Along the way, Ramsay's intense, distinctive visuals work a curious alchemy on Lionel Shriver's source novel, navigating a central conceit (the demon seed!) that in other hands might come across as crass and cheap. (I loved the night drive through a suburban Halloween, where skeletons, vampires and ghouls flit across the headlights beam like emissaries of the damned). Swinton, too, is terrific. She's flayed and haunted and hiding from her tormentors by the soup tins at the local supermarket – a scene that prompted a wholly inexplicable hoot of laughter from a lone man in the audience. Why the laughter? What was funny? Perversely, this isolated guffaw only added to the movie's uniquely creepy atmosphere; the sense of a world pitched off its axis.

I was less convinced by Sleeping Beauty, Julia Leigh's torpid, affectless wedding of fairytale archetypes with the tenets of high-end prostitution. This stars Emily Browning as Lucy, a pert young student who falls under the spell of a imperious madame-stroke-witch. Lucy's initial duties involve her sashaying about with her nipples on show, providing "silver service" dining to a gathering of wealthy old men, pouring the brandy and getting pawed by the clients. Harmless fun, in other words; the sort of saucy tomfoolery that takes place every night at those official Cannes jury dinners we hear about. Allegedly! Allegedly!

But then, wait. Things get weirder. Lucy allows herself to be drugged and starts reclining unconscious in bed while those same, supposedly harmless old men crawl in to ravish her. And so it goes. Leigh's film is precise, ponderous and borderline preposterous. The inherent danger in making a film about a numb, passive heroine, I suppose, is that you risk winding up with a film that is numb and passive itself.

Away from the screening rooms, the festival opens in a welter of industry deals and celebrity pop-ins. Look, there's jurors Robert De Niro, Uma Thurman and Jude Law out on the carpet. And look, there's Salma Hayek, drumming up business for her Shrek spin-off Puss-in-Boots. The official image at this years festival, meantime, shows Faye Dunaway in monochrome 60s mode. She gazes down, 12-ft high, above the Palais entrance. And look, here's Dunaway in coloured 21st-century mode, in town to showcase a restored version of film of hers from 1970, Puzzle of a Downfall Child. It's alarming. It's terrifying. A few years back I interviewed Faye Dunaway in London. The interview ended with her screaming that I had insulted her and me fleeing down the back stairs of a smart London hotel in what may well rank as the most ignominious exit ever effected by any journalist, ever. Now here she is again – possibly yards away, possibly drawing closer. Nothing else for it: I'm going to hide out by the soup tins.

• This article was amended on 13 May 2011. The original said that Faye Dunaway was in Cannes to attend the gala screening of her latest film. This has been corrected.